How can authoritarian states credibly signal their intentions in international crises? Nationalist, antiforeign protests are one mechanism by which authoritarian leaders can visibly demonstrate their domestic vulnerability. Because protests in authoritarian states are risky and costly to repress, the decision to allow or stifle popular mobilization is informative. The threat of instability demonstrates resolve, and the cost of concession increases the credibility of a tough stance. The danger of instability and escalation increases foreign incentives to make concessions and preserve the status quo. This logic helps explain the pattern of authoritarian tolerance and repression toward nationalist protest. A case study of two U.S.-China crises shows how China’s management of anti-American protests affected U.S. beliefs about Chinese resolve. …